texture paint changed my image to be black
I've just found the fix for this. I realize that it happened when i use 16bit TIFF file as texture map. So everytime i do a texture painting and save the image, it will save only my stroke, while the original image become black. Then i fix this by using 8bit, so i convert that 16bit into 8bit TIFF then reload that texture map and it solves my problem. I currently use 2.79 , so maybe this is a bug. 

Thanks.